Electrical machine with reduced windage

ABSTRACT

A rotating machine has a shaft rotatable about an axis, a rotor rotatable with the shaft, and a rotor end winding at an axial end of the rotor. A stator is spaced from the rotor and forms a gap therebetween. The stator comprises a stator winding. A fluid system directs fluid through to the stator. A baffle to diverts fluid away from the gap and toward the stator.

BACKGROUND OF THE INVENTION

This application relates to improvements in cooling rotating electricalmachines.

One type of rotating electrical machine is a generator. A generatorincludes a rotor driven by a power source to rotate relative to astator. The relative rotation of the rotor adjacent to the statorgenerates electrical power, thus converting mechanical energy intoelectrical energy. The electrical power is utilized for variouspurposes.

Another rotating electrical machine may be a motor. A motor includes arotor having conductors for carrying current to interact with magneticfields in a stationary stator. This electromagnetic interaction betweenthe rotor and stator generates forces that turn a shaft, convertingelectrical energy into mechanical energy for various purposes.

Both generators and motors have air gaps between their respective rotorsand stators.

Rotating electrical machines may rotate at high speeds and generatesignificant heat. The machines may be cooled by cooling liquid. Forliquid cooled high speed machines, there is a propensity for coolingfluid to enter the air gap between the rotor and stator. Fluid in theair gap may result in frictional loss causing reduced efficiency andreduced reliability.

SUMMARY OF THE INVENTION

A rotating machine has a shaft rotatable about an axis, a rotorrotatable with the shaft, and a rotor end winding at an axial end of therotor. A stator is spaced from the rotor and forms a gap therebetween.The stator comprises a stator winding. A fluid system directs fluid tothe stator. A baffle diverts fluid away from the gap and toward thestator.

These and other features may be best understood from the followingdrawings and specification.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows an example rotating machine.

FIG. 2 shows a sectional view of the example rotating machine.

FIG. 3 schematically shows the fluid path through the rotor end windingof the example rotating machine.

FIG. 4 schematically shows the fluid path with a baffle.

FIG. 5a shows a front view of an example baffle.

FIG. 5b shows a cross-sectional view of the example baffle in FIG. 5 a.

DETAILED DESCRIPTION

Referring to FIG. 1, an example rotating electrical machine 10 includesa shaft 12 that rotates about an axis “A.” A rotor 14 rotates with theshaft 12 relative to a stator 16 radially outward of the rotor 14. Thestator 16 may include stator windings 18 on its inner diameter. A gap 20is provided radially between the rotor 14 and the stator 16 allowing forrotation of the rotor. Through this rotation, the electrical machine 10converts mechanical energy into electrical energy. Although the exampleelectrical machine 10 is a generator, the electrical machine 10 could beany rotating machine, including a motor.

Because the operation generates significant heat, the example rotatingelectrical machine 10 is liquid cooled. As shown in FIG. 2, coolingfluid flows (flowpath F) through a hollow interior 22 of the shaft 12.The shaft 12 includes an orifice 24. Centrifugal force from rotationcauses the fluid to exit the shaft 12 through the orifice 24.

That fluid then flows radially outward through and around the rotor endwindings 26 (See FIG. 3), including between the plurality of coils 28,to cool the rotor end windings 26. The rotor end windings 26 areprovided at an axial end of the rotor windings 30 of rotor 14.Electromagnetic interaction between the rotor windings and the statorwindings 18 converts mechanical energy into electrical energy, as isknown by one of ordinary skill in the art. In the example, fluidcontinues to travel radially outward toward the stator windings 18 toprovide cooling to the stator windings 18.

Referring to FIG. 4, the fluid has a propensity to flow into the gap 20between the rotor 14 and the stator 16. Fluid in the gap 20 would causefrictional (windage) loss due to viscous shearing of the fluid withinthe gap during rotation, greatly reducing efficiency. A baffle 32 isthus placed adjacent to the gap 20 to divert fluid away from the gap 20.

The example baffle 32 is attached to the inner diameter of the statorwinding 18 and is axially outward of the rotor 14 and the gap 20. Thebaffle 32 includes an edge 34 extending radially outward as it extendsaxially away from the gap 20 to deflect fluid axially away from the gap20 and radially toward the stator winding 18. The cross section of theexample baffle 32 may be triangular in shape. The baffle 32 is thuspositioned such that the edge 34 is provided by the hypotenuse of thetriangular cross section, which is angled to deflect fluid axially awayfrom the gap 20 and toward the stator winding 18. The radially inner end35 of edge 34 is radially inward of the radially outward surface 37 ofrotor 14. While a triangular shape is shown, other shapes arecontemplated. In one embodiment, the edge 34 may be curved.

As shown in FIGS. 5a and 5b , the example baffle 32 extends around theentire circumference of the stator winding 18. As one alternativeembodiment, the baffle 32 may extend around a partial circumference ofthe stator winding 18.

In the example, referring back to FIG. 2, fluid exits the orifice 24 andflows radially outward through the end winding support 36 attached tothe axial end of the rotor 14. The end winding support 36 providessupport for the rotor end windings 26 and is radially between the shaft12 and the rotor end windings 26. The end winding support 36 includes achannel 38 aligned with the orifice 24 for directing fluid radiallyoutward toward the rotor end windings 26.

After the fluid travels around and through the rotor end windings 26, itcontinues to flow radially outward toward an end ring 40 configured tohold the rotor end winding assembly together. The fluid then flowsradially outward of the end ring 40 toward the stator winding 18,flowing either axially inward (flowpath f_(i)) or axially outward(flowpath f_(o)) of the end ring 40, as shown in FIG. 4. The fluid f_(i)has a propensity for entering the gap 20. Thus, the baffle 32 is placedbetween fluid path f_(i) and the gap 20 to divert fluid away from thegap and toward the stator winding 18.

Although the example disclosed is an electrical machine having woundrotors and stators, the features described are not limited to thosetypes of machines and may be used in any rotating machines.

Although an embodiment of this invention has been disclosed, a worker ofordinary skill in this art would recognize that certain modificationswould come within the scope of this invention. For that reason, thefollowing claims should be studied to determine the true scope andcontent of this invention.

I claim:
 1. A rotating machine, comprising: a shaft rotatable about anaxis and including an orifice; a rotor rotatable with said shaft; arotor end winding at an axial end of said rotor; an end winding supportattached to said axial end of said rotor, the end winding supportpositioned radially between the shaft and the rotor end winding toprovide support for the rotor end winding, the end winding supportincluding a channel aligned with the orifice; a stator spaced from saidrotor and forming a gap therebetween, said stator having a statorwinding; a fluid system configured to direct fluid through said orifice,through said channel, through said rotor end winding and to said statorwinding; a baffle attached to an inner diameter of said stator windingand disposed entirely axially outward of said rotor and said gap, saidbaffle positioned to divert fluid away from said gap and to said statorend winding, wherein said baffle includes an edge that extends axiallyaway from said gap and radially outward to provide a surface to divertsaid fluid, a radially inner end of said edge is radially inward of aradially outer surface of said rotor, and said baffle is triangular incross-section, and said edge is the longest edge of said triangularcross section; and an end ring radially outward of said rotor endwinding, wherein said baffle is configured to divert fluid flowingaxially inward of said end ring away from said gap.
 2. A rotatingmachine, comprising: a shaft rotatable about an axis and including anorifice; a rotor rotatable with said shaft; a rotor end winding at anaxial end of said rotor; an end winding support attached to said axialend of said rotor, the end winding support positioned radially betweenthe shaft and the rotor end winding to provide support for the rotor endwinding, the end winding support including a channel aligned with theorifice; a stator spaced from said rotor and forming a gap therebetween,said stator having a stator winding; a fluid system configured to directfluid through said orifice, through said channel, through said rotor endwinding and to said stator winding; a baffle attached to an innerdiameter of said stator winding and disposed entirely axially outward ofsaid rotor and said gap, said baffle positioned to divert fluid awayfrom said gap and to said stator end winding, wherein said baffleincludes an edge that extends axially away from said gap and radiallyoutward to provide a surface to divert said fluid, a radially inner endof said edge is radially inward of a radially outer surface of saidrotor, and said radially inner end of said edge is disposed axiallybetween said rotor end winding and said gap; and an end ring radiallyoutward of said rotor end winding, wherein said baffle is configured todivert fluid flowing axially inward of said end ring away from said gap.